Use of copolymers based on acrylamidoalkylsulfonic acids as thickeners in preparations comprising organic solvents

ABSTRACT

The invention relates to the use of copolymers consisting essentially of  
     a1) 1 to 50% by weight of the repeat structural unit of the formula (1)  
                 
 
      where n is an integer from 2 to 9 or  
     a2) 1 to 50% by weight of a mixture of the repeat structural unit of the formula (1) and of the repeat structural unit of the formula (2)  
                 
 
      where R, R 1  and R 2  may be identical or different and are hydrogen or a linear or branched alkyl or alkenyl group having in each case 1 to 30 carbon atoms, and  
     b) 49.99 to 98.99% by weight of the repeat structural unit of the formula (3)  
                 
 
      in which R 3  is hydrogen, methyl or ethyl, Z is (C 1 -C 8 )-alkylene and X is an ammonium, alkali metal or alkaline earth metal ion and  
     c) 0.01 to 8% by weight of crosslinking structures which originate from monomers having at least two olefinic double bonds, as thickeners in preparations comprising organic solvents.

[0001] The present invention relates to the use of water-soluble orwater-swellable copolymers based on acrylamidoalkylsulfonic acids andcyclic N-vinylcarboxamides or cyclic and linear N-vinylcarboxamides asthickeners in preparations comprising organic solvents.

[0002] Water-containing or solvent-containing multicomponent systems,such as solutions, emulsions or suspensions, are frequently adjusted tohigher viscosities or thickened because of economic or applicationreasons or because of the stability. Thus it is possible, for example,by increasing the viscosity of the external or internal phase of theemulsions or suspensions, to significantly prolong the time before thecomponents separate, which signifies increased storage time. In the caseof many products, increasing the viscosity also improves their uniformdistribution, in particular on uneven surfaces. This is true inparticular for hair care compositions, skin care compositions andpharmaceutical ointments on the skin. In the case of many technicalproducts, such as, for example, wallpaper strippers, paint removers oraircraft deicers, the increased viscosity prevents the product fromprematurely running off the surface to be treated. The more uniformdistribution and prolonged contact time increases the effectiveness. Inaddition to the application advantages mentioned, the high viscosity ofsuch preparations also offers advantages for the preparation, packaging,bottling and storage, and also for transportation. In particular, thethickening of acidic media is of importance here from a safetyviewpoint.

[0003] In general, the rheological properties during the preparation orformulation of cosmetic, pharmaceutical or technical preparations are adecisive criterion for the use of these products in practice. Thethickeners used should lead, even in the smallest possible amounts andin a wide pH range, to adequate thickening. The principal properties ofthe products, e.g. including their color, should not be changed.

[0004] Numerous thickener systems have been proposed in the specialistliterature for setting rheological properties of aqueous orsolvent-containing systems.

[0005] Known thickeners are, for example, polymers based on polyacrylicacid, e.g. ®Carbopols, carbomers, ammonium polyacrylates or sodiumacrylates copolymers. Also suitable are cellulose ethers, cellulosederivatives (e.g. carboxymethylcellulose, hydroxyethylcellulose),gelatins, starch and starch derivatives, sodium alginates, fatty acidpolyethylene glycol esters, agar agar, tragacanth or dextrins. Alsosuitable are polyvinyl alcohols, polyacrylamides, polyvinylpyrrolidone,polyvinyl methyl ether, polyethylene oxides, copolymers of maleicanhydride and vinyl methyl ether, and mixtures thereof.

[0006] Use is also made of long-chain polyethers together with fattyacid esters, e.g. polyethylene glycol 6000 distearate, polyethyleneglycol-polypropylene glycol monoethers, and reaction products ofpolyalcohols with fatty acids, e.g. pentaerythritol fatty acid esters.

[0007] However, the thickeners mentioned in the prior art are not freefrom disadvantages.

[0008] Thus, for example, the thickeners based on polyacrylic acid haveonly inadequate thickening ability in the strongly acidic pH range andin the case of compositions with a high content of organic solvents. Inaddition, the corresponding gels/formulation are sensitive to UVradiation and shearing and in addition impart a sticky feel to the skin.

[0009] Cellulose derivatives are very susceptible to bacteria. Theformation of “thread-drawing” gels is also undesired.

[0010] Fatty acid polyethylene glycol esters tend toward hydrolysis inthe presence of water. The insoluble fatty acids formed therein causeundesired clouding.

[0011] Thickeners of a natural origin (e.g. agar agar or tragacanth)have a greatly varying composition depending on their origin.

[0012] Surprisingly, it has now been found that copolymers based onacrylamidoalkylsulfonic acids and cyclic N-vinylcarboxamides or cyclicand linear N-vinylcarboxamides are highly suitable as thickeners forpreparations comprising organic solvents.

[0013] The invention therefore provides for the use of copolymersconsisting essentially of

[0014] a1) 1 to 50% by weight of the repeat structural unit of theformula (1)

[0015]  where n is an integer from 2 to 9 or

[0016] a2) 1 to 50% by weight of a mixture of the repeat structural unitof the formula (1) and of the repeat structural unit of the formula (2)

[0017]  where R, R¹ and R² may be identical or different and arehydrogen or a linear or branched alkyl or alkenyl group having in eachcase 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms, particularlypreferably 1 to 12 carbon atoms, and

[0018] b) 49.99 to 98.99% by weight of the repeat structural unit of theformula (3)

[0019]  in which R³ is hydrogen, methyl or ethyl, Z is (C₁-C₈)-alkyleneand X is an ammonium, alkali metal or alkaline earth metal ion and

[0020] c) 0.01 to 8% by weight of crosslinking structures whichoriginate from monomers having at least two olefinic double bonds, asthickeners in preparations comprising organic solvents.

[0021] The mixing ratio with regard to structural unit a2) can varywithin any desired limits.

[0022] Preferred copolymers comprise

[0023] 2 to 30% by weight, particularly preferably 3 to 15% by weight,of the structural units a1) or a2), preferably of the structural unita2), 69.5 to 97.5% by weight, particularly preferably 84.5 to 96.5% byweight, of the structural unit b) and 0.01 to 5% by weight, particularlypreferably 0.2 to 3% by weight, particularly preferably 0.5 to 2% byweight, of the structural unit c).

[0024] Particularly preferred structural units according to formula (1)are derived from N-vinylpyrrolidone.

[0025] Suitable structural units according to formula (3) are preferably2-acrylamido-2-methylpropanesulfonic acid, preferably the ammoniumsalts, particularly preferably the NH₄ ⁺ salt.

[0026] The crosslinking structural units c) are preferably derived fromallyl acrylate or allyl methacrylate, trimethylolpropane triacrylate,trimethylolpropane methacrylate, dipropylene glycol diallyl ether,polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinonediallyl ether, tetraallyloxyethane or other allyl or vinyl ethers ofmultifunctional alcohols, tetraethylene glycol diacrylate,triallylamine, trimethylolpropane diallyl ether, methylenebisacrylamideand/or divinylbenzene. Particular preference is given to allyl acrylate,allyl methacrylate, trimethylolpropane triacrylate and/ortrimethylolpropane methacrylate.

[0027] In particular, the crosslinking structures are derived frommonomers of the

[0028] formula (4)

[0029] in which R is hydrogen, methyl or ethyl.

[0030] The copolymers are preferably water-soluble or water-swellablecopolymers.

[0031] The copolymers are preferably prepared by free-radicalcopolymerization, preferably by precipitation polymerization,particularly preferably in tert-butanol. In this connection, themonomers corresponding to the formulae (1), (2) and (3) are preferablydissolved or dispersed in a protic solvent, then one or morecrosslinkers c) are added to this solution or dispersion and thepolymerization is started in a known manner by adding afree-radical-forming compound.

[0032] The polymerization reaction is preferably carried out in awater-soluble alcohol or a mixture of two or more alcohols having 1 to 6carbon atoms, preferably in tert-butanol. The water content of thealcohol or alcohol mixture should not exceed 10% by weight sinceotherwise formation of clumps may arise over the course of thepolymerization. The nature and the amount of solvent should be chosen insuch a way that the salt of acrylamidoalkylsulfonic acid correspondingto formula (3), in particular 2-acrylamido-2-methylpropanesulfonic acid,is largely soluble or dispersible therein. Largely soluble ordispersible is to be understood as meaning that no solid materialsettles out of the solution or dispersion even after the stirrer hasbeen switched off. The polymer produced in the course of the reactionshould, on the other hand, be largely insoluble in the chosen solvent orsolvent mixture. Largely insoluble is to be understood here as meaningthat a readily stirrable, pulpy polymer paste in which no clumps oragglutinations form arises during the course of the polymerization. Thefiltrate obtainable by filtering the paste with suction should have asolids content of at most 5% by weight. If the copolymers are soluble toa greater extent in the chosen solvent or solvent mixture, then clumpingmay arise upon drying the polymer paste.

[0033] The polymerization reaction itself is started in a manner knownper se by free-radical-forming compounds such as azoinitiators (e.g.azobisisobutyronitrile), peroxides (e.g. dilauryl peroxide) orpersulfates in the temperature range from 20 to 120° C., preferablybetween 40 and 80° C., and continues over a period of some 30 minutes toa few hours.

[0034] The property profile of the copolymers can be varied by varyingthe mixing ratio of the monomers and also the proportion of crosslinker.Thus, for example, the increased incorporation of ammonium salts of theacrylamidosulfonic acids can improve the thickening action of thepolymers. On the other hand, the incorporation of more cyclicN-vinylcarboxamide improves the electrolyte compatibility of thepolymers and their solubility in nonaqueous systems.

[0035] Particularly preferred copolymerized acrylamidopropylsulfonicacid salts are the NH₄ ⁺ salts. Instead of the ammonium salts, it isalso possible to use the free acrylamidopropylsulfonic acids and toproduce the ammonium salts by introducing ammonia prior to the additionof the remaining monomers.

[0036] The preparations preferably comprise 0.1 to 5% by weight,particularly preferably 0.5 to 2% by weight, especially preferably 0.7to 1.5% by weight, of copolymers.

[0037] The organic solvents are preferably polar-aprotic solvents,particularly preferably water-miscible polar-aprotic solvents.

[0038] Preference is given to monohydric alcohols, particularlypreferably those chosen from methanol, ethanol, propanol, isopropanol,n-butanol, isobutanol, t-butanol, benzyl alcohol, phenoxyisopropanol,phenylpropanol, diacetone alcohol, oleyl alcohol, ethoxyethanol, hexylalcohol, isobutoxypropanol, 4-methoxybutanol, methoxyethanol,methoxyisopropanol, methoxymethylbutanol, trimethylhexanol, especiallypreferably those having 1 to 6 carbon atoms, very particularlypreferably methanol, ethanol, propanol, isopropanol, n-butanol,isobutanol and t-butanol.

[0039] Preference is also given to polyhydric alcohols, particularlypreferably those chosen from the group glycerol, benzene glycol, butoxydiglycol, butoxyethanol, butanediol, butoxyisopropanol, butylene glycol,butyloctanol, pentylene glycol, hexanediol, propylene glycol, diethyleneglycol, dimethoxydiglycol, dipropylene glycol, glycol,1,2,6-hexanetriol, isopentyldiol, methoxydiglycol, methylpropanediol,neopentyl glycol, ethoxydiglycol, ethylhexanediol, hexylene glycol, veryparticularly preferably glycerol, propylene glycol, butylene glycol andglycol.

[0040] Preference is also given to ketones, esters, ethers, amides,sulfoxides, nitriles, O—, N— and S-heterocycles, preferably acetone,methoxyethanol acetates, triacetin (glycerol triacetate), amyl acetate,benzyl benzoate, benzyl laurate, butoxyethyl acetate, butyl acetate,butylene glycol propionate, butyl lactate, butyloctyl benzoate,butyloctyl salicylate, butyrolactone, C5-18 fatty acid triglycerides,PEG/PPG copolymers, propyl acetate, propylene carbonate, propyleneglycol butyl ether, propylene glycol propyl ether, tetrahydrofurfurylacetate, tetrahydrofurfuryl alcohol, thiolanediol, tributyl citrate,tributylcresylbutane, acetonitrile, THF (tetrahydrofuran), DMF(dimethylformamide), DMSO (dimethylsulfoxide), DBU(diaazabicycloundecane), pyridine, particularly preferably acetone,acetonitrile, THF (tetrahydrofuran) and DMF (dimethylformamide).

[0041] Also preferred are ethoxylated and/or propoxylated alcohols,particularly preferably ethoxylated and/or propoxylated alcohols with 1to 20 mol of ethylene oxide and/or 1 to 20 mol of propylene oxide,especially preferably ethoxylated and/or propoxylated alcohols chosenfrom polypropylene glycol-7, polypropylene glycol-10, PPG-2-buteth-3,PPG-3-buteth-5, PPG-5-buteth-7, PPG-7-buteth-10, PPG-12-buteth-16,PPG-15-buteth-20, PPG-20-buteth-20, PPG-2-butyl ether, PPG-3-butylether, PPG-24-glycereth-24, PPG-10-glyceryl ether, glyceryl ether,PPG-2-methyl ether, PPG-3-methyl ether, PPG-2-methyl ether acetate,PPG-2-propyl ether, propylene glycol butyl ether, propylene glycolpropyl ether, methoxy PEG-10, methoxy PEG-16, buteth-3, sorbeth-6 andsorbeth-20.

[0042] Preference is also given to polyethylene glycols, particularpreference to polyethylene glycols with a molecular mass of less than 2000 g/mol, particularly preferably polyethylene glycols with a molecularmass between 200 and 600 g/mol.

[0043] Mixtures of organic solvents may be advantageous depending on theapplication and are thus expressly within the meaning of the invention.

[0044] The solvent content of the preparations can be 5 to 99.9% byweight, based on the finished preparation.

[0045] Surprisingly, the copolymers exhibit very good thickeningperformance even in the range of high solvent contents. Preparationswith high solvent contents preferably comprise 40 to 95% by weight,particularly preferably 50 to 85% by weight, of solvents.

[0046] Preparations with low contents of solvents preferably comprise 5to 30% by weight of solvents. Preparations with low contents of solventsexhibit a high viscosity stability, particularly in the pH range 3 to 6,preferably 3 to 5.

[0047] The preparations may contain water or be free from water.However, particularly in the case of cosmetic, dermatological andpharmaceutical preparations, a water content of from 30 to 80% byweight, based on the finished preparations, is advantageous.

[0048] The preparations preferably have a pH in the range 3 to 10,particularly preferably 4 to 9.

[0049] The use of the copolymers as thickeners is particularly suitablefor cosmetic, dermatological and pharmaceutical preparations.

[0050] The cosmetic compositions may be rinse-off products, e.g.shampoos, shower preparations, shower gels, foam baths, or else leave-onproducts, e.g. skincare compositions, such as day creams, night creams,care creams, nutrient creams, body lotions, ointments, sunscreens,lipcare compositions and deodorants. They may also be surfactant-freeaqueous-solvent-containing compositions and emulsions, e.g. hair curesand rinses, hair gels, permanent waving compositions, hair colorants andthe like.

[0051] The cosmetic, dermatological and pharmaceutical preparationsaccording to the invention can comprise, as further auxiliaries andadditives, all customary surfactants, oily substances, emulsifiers andcoemulsifiers, superfatting agents, stabilizers, biogenic activeingredients, preservatives, pearlizing agents, dyes and fragrances,opacifiers, further thickeners and dispersants, protein derivatives,e.g. gelatin, collagen hydrolysates, natural- and synthetic-basedpolypeptides, egg yolk, lecithin, lanolin and lanolin derivatives, fattyalcohols, silicones, deodorizing compositions, substances with akeratolytic and keratoplastic action, enzymes, antimicrobial agents andcarrier substances.

[0052] However, the use according to the invention is not limited tocosmetic, dermatological and pharmaceutical preparations. Rather, thepreparations may, for example, also be paint removers, lacquer removers,aircraft deicers, hard surface cleaners, window cleaners, emulsionpaints, printing inks and pastes.

[0053] An essential advantage of the use according to the invention isthe high viscosity stability of the preparations toward pH changes. Afurther advantage is the high UV stability of the preparations.

[0054] The invention also provides a method of thickening preparationscomprising organic solvents, which comprises adding to the preparationsat least one copolymer consisting essentially of

[0055] a1) 1 to 50% by weight of the repeat structural unit of theformula (1)

[0056]  where n is an integer from 2 to 9 or

[0057] a2) 1 to 50% by weight of a mixture of the repeat structural unitof the formula (1) and of the repeat structural unit of the formula (2)

[0058] where R, R¹ and R² may be identical or different and are hydrogenor a linear or branched alkyl or alkenyl group having in each case 1 to30, preferably 1 to 20, particularly 1 to 12 carbon atoms, and

[0059] b) 49.99 to 98.99% by weight of the repeat structural unit of theformula (3)

[0060]  in which R³ is hydrogen, methyl or ethyl, Z is (C₁-C₈)-alkyleneand X is an ammonium, alkali metal or alkaline earth metal ion and

[0061] c) 0.01 to 8% by weight of crosslinking structures whichoriginate from monomers having at least two olefinic double bonds.

[0062] The examples below serve to illustrate the invention in moredetail without, however, limiting it thereto.

[0063] 1) Preparation of the copolymers:

[0064] Copolymer 1:

[0065] 490.5 g of tert-butanol and 11.5 g of water were introduced intoa 1 000 ml flask fitted with anchor stirrer, reflux condenser, internalthermometer, and feed option for N₂ and NH₃. 80.75 g of2-acrylamido-2-methylpropanesulfonic acid were then introduced anddispersed with vigorous stirring, clouding of the solvent beingretained. Over a period of 30 minutes, 6.64 g of ammonia was introducedinto the gas head space, and the mixture was stirred for at least afurther 30 minutes until the pH was 6-7. 4.10 g of N-vinylpyrrolidoneand 0.8 g of allyl methacrylate were added, and the receiver was in eachcase then rinsed with tert-butanol (about 6 ml) in order to minimizelosses during the addition. The reaction mixture was then heated to atemperature of T=60° C., the reaction mixture being rendered inert bythe simultaneous introduction of N₂. After a temperature of T=60° C. hadbeen reached, 1.0 g of dilauryl peroxide were added. The reactionstarted directly after the addition of the initiator, which was evidentfrom an increase in the temperature and from flocculation of thepolymer. Approximately 15 minutes after the polymerization reaction hadstarted, the nitrogen feed was switched off. Approximately 30 minutesafter the addition of the dilauryl peroxide the temperature reached amaximum (about 65-70° C.). For a further 30 minutes after this maximumhad been passed through the mixture was refluxed and then stirred underthese conditions for two hours. The contents of the reaction vesseladopted a pulp-like consistency over the course of the reaction, but wasstill readily stirrable. The mixture was then cooled to room temperatureand the solid was filtered off with suction.

[0066] The paste was dried at 60-70° C. in a vacuum drying cabinet for24 hours, giving 92.2 g of a fine white powder.

[0067] Copolymer 2:

[0068] The reaction was carried out analogously to example 1, exceptthat instead of allyl methacrylate, 1.65 g of trimethylolpropanemethacrylate were used.

[0069] Copolymer 3:

[0070] The reaction was carried out analogously to example 1, but using35 g of 2-acrylamido-2-methylpropanesulfonic acid, 55 g ofN-vinylpyrrolidone and 1.9 g of trimethylolpropane triacrylate asmonomers.

[0071] Copolymer 4:

[0072] The reaction was carried out analogously to example 1, but using77.5 g of 2-acrylamido-2-methylpropanesulfonic acid, 8.9 g ofN-vinylpyrrolidone, 4.2 g of N-vinylformamide and 1.8 g oftrimethylolpropane triacrylate as monomers.

[0073] 2) Applications:

[0074] Tables 1, 2 and 3 show the thickening performance of thecopolymers in solvent-containing preparations. The comparison used was acommercially available thickener based on acrylic acid (Carbopol® 980from Goodrich). To measure the viscosity, aqueous gels were preparedfrom copolymer 1 and Carbopol® 980, said gels then being adjusted to thedesired solvent concentration by adding polar-aprotic solvents. Thethickener content was always 1.0% by weight. The viscosity was measuredat 20° C. using a Brookfield viscometer model RVT at 20 rpm. TABLE 1Viscosities (mPas) of 1.0% by weight of copolymer 1 and 1.0% by weightof  ®Carbopol 980 in ethanol/demineralized water andacetone/demineralized water mixtures; pH 5.5 to 6 Viscosities (mPas)Viscosities (mPas) Mixtures Copolymer 1  ®Carbopol 980 EtOH/demin. water0:10 50000 61000 1:9 49000 59000 2:8 48000 48000 3:7 46000 <100 4:641000 <100 5:5 33000 <100 6:4 23500 <100 7:3 14000 <100 8:2 5000 <100Acetone/demin. water 0:10 50000 61000 1:9 48300 65500 2:8 46400 660003:7 44000 50000 4:6 41000 <100 5:5 36000 <100 6:4 27000 <100

[0075] TABLE 2 Viscosities (mPas) of 1.0% by weight of copolymer 1 and1.0% by weight of  ®Carbopol 980 in ethanol/demineralized water (1:9) atvarious pHs Viscosities (mPas) Viscosities (mPas) pH Copolymer 1 ®Carbopol 980 7.0 49000 59000 6.0 48000 48000 5.0 47000 25000 4.5 4750010000 4.0 48000 <100 3.5 35000 <100 3.0 29000 <100

[0076] TABLE 3 Viscosities (mPas) of 1.0% by weight of copolymer 1 in1:1 mixtures of various solvents with water; pH 5.5 to 6 MixtureViscosity (mPas) Appearance Propylene glycol/demin. water 55000 cleargels PEG 400/demin. water 18200 clear gels Glycol/demin. water 46800clear gels Glycerol/demin. water 55000 clear gels Acetonitrile/demin.water 23500 cloudy gel DMF/demin. water 39500 clear gel DMSO/demin.water 63500 cloudy gel

[0077] It can be seen that the copolymers have a high thickeningperformance in solvent-containing preparations. This applies inparticular in the range of high solvent contents. In the range of lowersolvent contents, the thickening performance is very good particularlyin the acidic pH range.

1. A process for thickening a preparation comprising an organic solventsaid process comprising adding for the preparation of copolymers,consisting essentially of a1) 1 to 50% by weight of the repeatstructural unit of the formula (1)

 where n is an integer from 2 to 9 or a2) 1 to 50% by weight of amixture of the repeat structural unit of the formula (1) and of therepeat structural unit of the formula (2)

 where R, R¹ and R² may be identical or different and are hydrogen or alinear or branched alkyl or alkenyl group having in each case 1 to 30carbon atoms, and b) 49.99 to 98.99% by weight of the repeat structuralunit of the formula (3)

 in which R³ is hydrogen, methyl or ethyl, Z is (C₁-C₈)-alkylene and Xis an ammonium, alkali metal or alkaline earth metal ion and c) 0.01 to8% by weight of crosslinking structures which originate from monomershaving at least two olefinic double bonds.
 2. The process of claim 1,wherein the copolymers comprise 2 to 30% by weight of the structuralunits a1) or a2), 69.5 to 97.5% by weight of the structural unit b) and0.01 to 5% by weight of the structural unit c).
 3. The process of claim1, wherein the copolymers comprise the structural unit a2).
 4. Theprocess of claim 1, wherein the structural unit according to formula (1)is derived from N-vinylpyrrolidone.
 5. The process of claim 1, whereinthe structural unit according to formula (3) is derived from2-acrylamido-2-methylpropanesulfonic acid or an ammonium salt thereof.6. The process of claim 1, wherein the structural units c) are derivedfrom the group consisting of allyl acrylate, allyl methacrylate,trimethylolpropane triacrylate, trimethylolpropane methacrylate, andmixtures thereof.
 7. The process of claim 1, wherein the copolymers areprepared by precipitation polymerization in tert-butanol.
 8. The processof claim 1, wherein the preparation comprises 0.1 to 5% by weight ofcopolymers, based on a finished preparation.
 9. The process of claim 1,wherein the organic solvent comprises polar-aprotic solvent.
 10. Theprocess of claim 9, wherein the organic solvent is selected from thegroup consisting of monohydric alcohols, polyhydric alcohols, ketones,esters, ethers, amides, sulfoxides, nitrites, O—, N—and S-heterocycles,ethoxylated alcohols, propoxylated alcohols polyethylene glycols, andmixtures thereof.
 11. The process of claim 10, wherein the organicsolvent is selected from the group consisting of methanol, ethanol,propanol, isopropanol, n-butanol, isobutanol, t-butanol, glycerol,propylene glycol, butylene glycol, glycol, acetone, acetonitrile,tetrahydrofuran, dimethylformamide, and mixtures thereof.
 12. Theprocess of claim 1, wherein the preparation comprises 5 to 99.9% byweight of organic solvent, based on a finished preparation.
 13. Theprocess of claim 1, wherein the preparation comprises 40 to 95% byweight of the organic solvent, based on a finished preparation.
 14. Theprocess of claim 1, wherein the preparation comprises 5 to 30% by weightof organic solvent, based on a finished preparation and the finishedpreparation has a pH ranging from 3 to
 6. 15. The process of claim 1,wherein the preparation further comprises 30 to 80% by weight of water,based on the finished preparation.
 16. The process of claim 1, whereinthe preparation has a pH of from 4 to
 9. 17. The process of claim 1,wherein the preparation is selected from cosmetic, dermatological, andpharmaceutical preparations.
 18. A method of thickening preparationscomprising organic solvents, which comprises adding to the preparationsat least one copolymer consisting essentially of a1) 1 to 50% by weightof the repeat structural unit of the formula (1)

 where n is an integer from 2 to 9 or a2) 1 to 50% by weight of amixture of the repeat structural unit of the formula (1) and of therepeat structural unit of the formula (2)

 where R, R¹ and R² may be identical or different and are hydrogen or alinear or branched alkyl or alkenyl group having in each case 1 to 30carbon atoms, and b) 49.99 to 98.99% by weight of the repeat structuralunit of the formula (3)

 in which R³ is hydrogen, methyl or ethyl, Z is (C₁-C₈)-alkylene and Xis an ammonium, alkali metal or alkaline earth metal ion and c) 0.01 to8% by weight of crosslinking structures which originate from monomershaving at least two olefinic double bonds said cross linking structuresselected from the group consisting of allyl acrylate, allylmethacrylate, trimethylolpropane triacrylate, trimethylolpropanemethacrylate, and mixtures thereof wherein the organic solvents comprisea water-miscible polar-aprotic solvent.